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Here's a look at the 10 most common phobias as rated by the National Institute of Mental Health, and how these phobias could offer the investment opportunity of a lifetime.

Do you have a large number of strange fears that you keep to yourself, or perhaps only a close few friends or family members know about?

If you answered yes, then chances are you could be among the 8.7% of the U.S. adult population that the National Institute of Mental Health lists as having a specific phobia that has lasted for at least 12 months. To put that into a different context, the NIMH estimates that just shy of 21 million adults in the U.S. (based on 2012 U.S. Census Bureau figures) have some form of prevalent specific phobia.

I guess I should warn that if you have phobophobia, the phobia of phobias, or hippopotomonstrosesquippedaliophobia, which is a fear of long words and an irony in and of itself, then you may want to turn back now.

If, however, you're ready to face your worst fears, as well as those of some 21 million other Americans, we'll take a closer look at the nation's 10 most common phobias, as determined by a NIMH study and chronicled by StatisticBrain.

The 10 most common phobias According to the NIMH, the 10 most common phobias are:

1. Glossophobia -- the fear of public speaking.

2. Necrophobia -- the fear of death or dying.

3. Arachnophobia -- the fear of spiders.

4. Myctophobia -- the fear of darkness.

5. Acrophobia -- the fear of heights.

6. Sociophobia -- the fear of socializing or being in a crowded place.

I'm not ashamed to admit that I'm among the some 21 million adults who suffers from at least one of these phobias on a prevalent basis despite the fact that a number of these present little to no life-threatening harm to individuals. In fact, several of the most common phobias will never take place and are considered insignificant when it comes to the ability to affect a person's health.

What's also rather unique about phobia sufferers, myself included, is that a vast majority go without treatment, either from the embarrassment of admitting they have phobias to their doctor or family members, or the simple fact that some choose not to pay the fees associated with a doctor's visit and the subsequent prescribed medication.

A unique opportunity, revealed However, another way of looking at this is that nearly 14 million people in this country are going untreated for largely irrational phobias, representing an opportunity of immense growth for the health care industry.

Keep in mind the context of my statement doesn't assume there's a pharmaceutical fix for every phobia, because clearly that isn't the case. However, the Patient Protection and Affordable Care Act, known better as Obamacare, could be the impetus that helps reduce the prevalence of chronic or debilitating phobias by encouraging doctor's visits and the use of pharmacologic solutions.

Although Obamacare has been a highly polarizing law, it will encourage more Americans to frequent their doctor for preventive care visits. Therefore, more people with health insurance -- either through the legal requirement to purchase health insurance, or by qualifying for government-sponsored Medicaid -- should translate into better mental care, more prescriptions written, and hopefully a less anxious society overall.

Who might benefit from a "war on phobias?"Clear beneficiaries in tackling this monstrous issue would be physicians and outpatient clinics that would be expected to deal with an increasing number of patients. Obamacare is aimed at improving access to health care, so the number of doctor visits for anxiety-related disorders is also likely to rise.

While few individual stocks encompass a broad network of outpatient clinics, a medical real estate investment trust like Ventas (NYSE:VTR) does. Ventas, a property owner of hospitals, nursing facilities, and a variety of other medical office buildings, would be expected to command higher rent prices per square foot as the number of office visits increases. This is one of the primary assumptions under Obamacare, and a big reason why Ventas has been on a buying spree recently that resulted in record funds from operation for the medical REIT in the third quarter. Also, as a REIT it's required to pay out at least 90% of its profit in the form of a dividend in exchange for a favorable tax status. This means investors will enjoy nearly a 5% yield!

In addition to doctor visits, it's quite conceivable that a number of these 14 million people if properly diagnosed will receive a pharmaceutical prescription. That means a boost in pharmacy sales, whether it's for a branded or generic drug, for Walgreen(NASDAQ:WBA) and CVS Caremark(NYSE:CVS). Both drugstores have witnessed tough front-end sales comparisons as they've had to resort to loyalty rewards and discounting in order to drive foot traffic for those items. Pharmacy sales and consumer loyalty is where those rewards will pay their dividends. As national drugstores, both should be primary beneficiaries of Obamacare and would almost certainly see a positive top- and bottom-line benefit if even a fraction of these 14 million Americans visited their physician more often and received a prescription.

Finally, individual anxiety disorder drugmakers would be expected to benefit. The kicker with most anxiety and social disorder drugs is that many brand-name therapies have long since come off patent, meaning the most effective way for patients to receive assistance and for investors to benefit is through generic drugs.

The generic form of Pfizer's Xanax, for example, a treatment for general anxiety, social anxiety, and a number of phobias, is manufactured by Novartis' (NYSE:NVS) generic subsidiary Sandoz International. In terms of application, Xanax and its biosimilars are still the most prescribed anti-anxiety medications available, potentially giving Novartis' Sandoz a leg up on the competition.

Similar to Xanax is Wyeth's Ativan (Wyeth was purchased by Pfizer) which lost its patent protection a long time ago, and is targeted at general anxiety, phobias, and panic attacks. The drug itself is made by a number of generic suitors, including Mylan(NASDAQ:MYL). Keep in mind that while generic producers such as Mylan may have smaller margins than their branded pharmaceutical counterparts, their demand and pipelines are always full because of the attractive price point of generics and the finite period of branded drug exclusivity.

Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

Author

A Fool since 2010, and a graduate from UC San Diego with a B.A. in Economics, Sean specializes in the healthcare sector and investment planning. You'll often find him writing about Obamacare, marijuana, drug and device development, Social Security, taxes, retirement issues and general macroeconomic topics of interest. Follow @TMFUltraLong